1. Field of Invention
In several embodiments, the invention relates to a light pipe based color splitting and guiding system in which incoming broad spectrum light is split into its component colors and guided to the individual imagers through a series of light pipes, beam splitters, and prisms.
2. Description of the Related Art
Projection displays work by projecting light onto a screen. The light is arranged in patterns of colors or brightness and darkness or both. The patterns are viewed by a viewer who assimilates them by associating the patterns with images with which the viewer may already be familiar, such as characters or faces. The patterns may be formed in various ways. One way to form patterns is by modulating a beam of light with a signal representative of a stream of information.
Polarized light may be modulated by filtering it with polarized filters. Polarized filters will pass light, in general, if their polarization matches the polarization of incident light, and reject it if their polarization conflicts with the polarization of incident light. A liquid crystal display (LCD) imager is an example of a polarized filter that may be used in LCD-type projection displays in this way. The LCD imager may include pixels that are modulated by altering their polarization to either match or differ from the polarization of incident light. The light input to the LCD imager is also polarized such that when the polarization of selected pixels differs from that of the input light, the selected pixels will be darkened. The pattern of unchanged and darkened pixels may be projected onto a screen as the presence or absence of light. If the pixels are modulated with information in a pattern with which a viewer is familiar, the viewer may recognize the pattern when it is projected onto the screen.
Broad spectrum, or white, light emitted from a light source in a projection display engine is directed to the LCD imagers through a series of optical components such as mirrors, filters, and lenses, as shown in FIG. 1. These optical components separate the white light from the light source into its respective primary colors, usually red (R), green (G), and blue (B). These components can be quite expensive. Although projection systems with LCD imagers have been used commercially, the cost of the components is high, and precise alignment of the components is critical to their operation.
As shown in FIG. 1, white light 12 emitted from a light source 10 is collimated by lenses 14, 16, and 18, reflected by respective color filters 20 and 22, and directed towards LCD panels 30, 32, and 34. As seen from in FIG. 1, the position of LCD panels 30, 32, and 34 can be at a distance from light source 10 and as a result, additional lenses 24, 26, and 28 may be required to re-collimate the beam. The alignments of all these components relative to one another must be very accurate in order to couple light efficiently from light source 10 to LCD panels 30, 32, and 34 and minimize losses.
Furthermore, fixturing for the components to maintain their alignment can be quite costly. It would be desirable if a projection system could be built with fewer or less expensive components. It would further be desirable if a projection system could be built that was less sensitive to mis-alignment of individual components. As a result, there is a need for a system to perform polarization conversion with high efficiency, simple configurations and lower costs. Therefore, there exists a need for a projection engine configuration such that the light can be processed with simpler system requirements and reduced costs.